Structure of the functional interleukin-2 receptor: Evidence for the association of human p55 and murine p75 molecules in a mouse T cell line

The structural basis of the high affinity interleukin-2 receptorwhich was previously reconstituted in a cultured murine T cellline, EL4 by expressing either wild-type Tac antigen complementaryDNA (cDNA) or a chimeric cDNA was characterized. The chimericcDNA encodes a membrane portion whose extracellular portionconsists of that of Tac antigen whereas transmembrane and cytoplasmicportions consists of those the human insulin beta chain. TheTac antigen/anti-Tac antibody complex was treated by chemicalcrosslinking reagents, purified by goat anti-mouse immunoglobulin(lg), and was analysed by SDS–PAGE. We here demonstrated the presence in mouse EL4 transfectantsof a novel membrane protein which is closely associated withthe products of transfected cDNAs in the absence of interleukln-2.The protein is 75 kDa in size and is detected in cells whichexpress high affinity interieukln-2 receptor but not in cellswhich only express low affinity interleukin-2 receptor. Thetransmembrane region and the cytoplasmic region of Tac antigenis not necessary for the formation of the complex consistingof Tac antigen and 75 kDa molecule, indicating that a murine75 kDa molecule associates with Tac antigen extra-cellularly.     

Antigenic variation of the Epstein–Barr virus nuclear antigen EBNA1 as revealed by monoclonal antibodies

The Epstein–Barr virus (EBV) nuclear antigen EBNA1 plays an essential role in the replication of EBV episomes in latently infected cells and is the only viral protein that is consistently expressed in all programs of latent EBV gene expression. In this study, four monoclonal antibodies (MoAbs) directed to a region (amino acid residues 442–530) of EBNA1 were generated. Competitive enzyme-linked immunosorbent assay (ELISA) experiments using biotinylated MoAbs showed that they recognized distinct epitopes. Reactivity of these MoAbs with various laboratory EBV strains and field EBV isolates was shown to be heterogeneous in that EBNA1 from certain strains (isolates) was recognized and that from others was not. All four MoAbs showed such heterogeneous reactivity, and moreover, each MoAb showed a distinct spectrum of reactivity with these EBV strains (isolates). These results demonstrate an extensive structural variation in this region of EBNA1 as predicted by previous sequencing studies. These MoAbs will be useful as probes to dissect this structural heterogeneity of EBNA1.     

Skeletal muscle metabolism during short duration high-intensity exercise: influence of creatine supplementation

Seven male subjects performed repeated bouts of high-intensity exercise, on a cycle ergometer, before and after 6 d of creatine supplementation (20 g Cr H₂O day^-1). The exercise protocol consisted of five 6-s exercise periods performed at a fixed exercise intensity, interspersed with 30-s recovery periods (Part I), followed (40 s later) by one 10 s exercise period (Part II) where the ability to maintain power output was evaluated. Muscle biopsies were taken from m. vastus lateralis at rest, and immediately after (i) the fifth 6 s exercise period in Part I and (ii) the 10 s exercise period in Part II. In addition, a series of counter movement (CMJ) and squat (SJ) jumps were performed before and after the administration period. As a result of the creatine supplementation, total muscle creatine [creatine (Cr) + phosphocreatine (PCr)] concentration at rest increased from (mean + SEM) 128.7 (4.3) to 151.5 (5.5)mmolkg^_1 dry wt (P < 0.05). This was accompanied by a 1.1 (0.5) kg increase in body mass (P < 0.05). After the fifth exercise bout in Part I of the exercise protocol, PCr concentration was higher [69.7 (2.3) vs. 45.6 (7.5) mmol kg“‘ dry wt, P < 0.05], and muscle lactate was lower [26.2 (5.5) vs. 44.3 (9.9) mmol kg”¹ dry wt, P < 0.05] after vs. before supplementation. In Part II, after creatine supplementation, subjects were better able to maintain power output during the 10-s exercise period (P < 0.05). There was no change in jump performance as a result of the creatine supplementation (P > 0.05). These findings show that enhanced fatigue resistance during short duration high-intensity exercise following creatine supplementation is associated with a greater availability of PCr and a lower accumulation of lactate in the muscle. The finding that jump performance was not enhanced suggests that short-term creatine feeding does not influence peak power output.     

The expression of Rho proteins decreases with human brain tumor progression: Potential tumor markers

Astrocytic tumors are the most common human brain tumors. Establishment of tumor grade is a key determinant both in the choice of a therapeutic approach and in the prognosis. The diagnosis of astrocytic tumors is currently determined following histopathological analysis. The identification of molecular markers would offer a complementary tool for characterizing tumors with respect to their clinical behavior. In this study we determined the expression levels of 3 small GTP binding proteins (RhoA, RhoB and Rac1), of their inhibitor RhoGDI and of caveolin-1 in 24 human astrocytic tumors of grades I to IV. Our results demonstrated that the expression of RhoA and RhoB decreased significantly in all brain tumors studied and was inversely related with tumor of grade II to IV malignancy. The amount of caveolin-1 immunodetected was not significantly different from normal brain samples while the Rac1 expression level was diminished in astrocytic tumors of grades III and IV. Our finding that RhoA and RhoB expression levels are correlated to tumor malignancy suggests that they may serve as novel and efficient diagnostic markers for astrocytic brain tumors of histological grade II to IV and complement currently applied histopathological analysis.     

Defective suppression of Th2 cytokines by CD4+CD25+ regulatory T cells in birch allergics during birch pollen season

BACKGROUND: CD4(+)CD25+ regulatory T cells suppress proliferation and cytokine production by human T cells both to self-antigens and exogenous antigens. Absence of these cells in human newborns leads to multiple autoimmune and inflammatory disorders together with elevated IgE levels. However, their role in human allergic disease is still unclear. OBJECTIVE: This study aimed to evaluate the capacity of CD4(+)CD25+ regulatory T cells to suppress proliferation and cytokine production outside and during birch-pollen season in birch-allergic patients relative to non-allergic controls. METHODS: CD4+ cells were obtained from blood of 13 birch-allergic patients and six non-allergic controls outside pollen season and from 10 birch-allergic patients and 10 non-allergic controls during birch-pollen season. CD25+ and CD25- fractions were purified with magnetic beads and cell fractions, alone or together in various ratios, were cultured with antigen-presenting cells and birch-pollen extract or anti-CD3 antibody. Proliferation and levels of IFN-gamma, IL-13, IL-5 and IL-10 were measured by thymidin incorporation and ELISA, respectively. Numbers of CD25+ cells were analysed by flow cytometry. RESULTS: CD4(+)CD25+ regulatory T cells from both allergics and non-allergics potently suppressed T cell proliferation to birch allergen both outside and during birch-pollen season. However, during season CD4(+)CD25+ regulatory T cells from allergic patients but not from non-allergic controls were defective in down-regulating birch pollen induced IL-13 and IL-5 production, while their capacity to suppress IFN-gamma production was retained. In contrast, outside pollen season the regulatory cells of both allergics and non-allergic controls were able to inhibit T-helper 2 cytokine production. CONCLUSION: This is the first study to show differential suppression of Th1 and Th2 cytokines, with CD4(+)CD25+ regulatory T cells from birch-pollen-allergic patients being unable to down-regulate Th2, but not Th1 responses during birch-pollen season.     

人胎儿脊髓神经肽Y样神经元及其纤维的发育和分布的免疫细胞化学研究

人工流产胎儿标本２３例，孕龄１０～４１周，用免疫组织化学ＡＢＣ法，研究人胎儿脊髓神经肽Ｙ样神经元的发育和分布。结果在胎龄第１０周，发现脊髓后角浅层（ＲｅｘｔｄⅠ、Ⅱ层）已有神经肽Ｙ样免疫阳性神经元胞体存在，且阳性神经元总数随胎龄的增加而递增，并向后角深层（ＲｅｘｅｄⅢ～Ⅳ层）扩展神经肽Ｙ样阳性纤维，在胎龄第１０周，不仅出现于脊髓的灰质和白质，而且见于脊髓的被膜。随胎龄的增长，免疫阳性反应纤维相对集中于脊髓的植物性神经中枢的所在部位，揭示在妊娠早期，神经肽Ｙ可能与脊髓植物神经元的发育及其功能的调节有关。     

Augmentation of antigen-specific lymphoproliferative responses in vitro by biological response modifiers.

The detection of antigen-specific T cell responsiveness, particularly of resting memory lymphocytes, in cultures of peripheral blood mononuclear cells (PBMC) may be hampered by a less than optimal antigen presentation in vitro. Augmented sensitivity of the test system may be achieved by the addition of reagents with a beneficial effect on lymphocyte and antigen-presenting cell (APC) functions. In this study the effect of several biological response modifiers on antigen-specific T cell proliferation was determined, using nickel sulphate and tetanus toxoid as test antigens. IL-1 alpha (100 U/ml), interferon-gamma (IFN-gamma) (10 U/ml), and indomethacin (2 microM) were found to significantly enhance nickel-induced proliferation in PBMC cultures from nickel-hypersensitive donors (n = 6). Tetanus-induced proliferation (n = 5) was similarly enhanced, both by the above supplements and by the addition of polyethylene glycol (PEG) or a neuraminidase treatment of the PBMC before culture. The addition to PBMC cultures of a combination of IL-1 alpha (30 U/ml), IFN-gamma (10 U/ml), and indomethacin (2 microM) is recommended to specifically enhance antigen-induced lymphoproliferative signals.     

Antibodies to hepatitis E virus among chinese patients with acute hepatitis in Taiwan

The prevalence of antibodies to hepatitis E virus (anti-HEV) was investigated in patients with acute hepatitis, and correlated with the clinical features. Sera from 110 patients with acute hepatitis and 60 healthy controls were tested for anti-HEV, antibody to hepatitis C virus (anti-HCV), and hepatitis B surface antigen (HBsAg). There were significant differences in the prevalence of anti-HEV, anti-HCV, and HBsAg between patients and controls (21.8% vs. 0%, 16.3% vs. 1.6% and 58.1% vs. 18.0%, respectively). Anti-HEV was detected in 6 (25.0%) of 24 patients with anti-HCV, 6 (9.3%) of 64 patients with HBsAg, and another 6 (22.2%) of 27 patients with acute hepatitis non-A, non-B, non-C. Anti-HEV was found in 15 men and three women, whose ages ranged from 34 to 75 (median, 57) years old. The median age of patients with anti-HEV was older than that in patients without this antibody (57 vs. 38 years; P = 0.001). The prevalence of anti-HEV in patients with anti-HCV alone (35.2%) was higher than that (11.1%) in patients with HBsAg alone (P = 0.03). Compared to patients without anti-HEV, HEV-infected patients had a higher frequency of travel to a foreign country (P = 0.0001), had a lower HBsAg rate (P = 0.019), and had higher serum alkaline phosphatase levels (P = 0.04) and gamma-glutamyl transpeptidase levels (P = 0.01). In conclusion, HEV infection occurs in 22.2% of patients with acute hepatitis non-A, non-B, non-C. HEV superinfection may occur in patients with chronic hepatitis B or C virus infection. © 1994 Wiley-Liss, Inc.     

Rheumatoid arthritis may be primarily associated with HLA-DR4 molecules sharing a particular sequence at residues 67–74

Genomic typing of in vitro amplified DNA with sequence-specific oligonucleotide (SSO) probes was performed for DRB1, DQA1, DQB1, DPA1 and DPB1 alleles in 54 random Norwegian rheumatoid arthritis (RA) patients and 181 healthy controls. DRB1 alleles encoding the serological specificity DR4 were found in 80% of the patients, compared to 34% of the controls (relative risk = 7.9, p less than 0.0001). All DR4-positive RA patients carried either DRB1*0401 (Dw4), 0404 (Dw14), or 0405 (Dw15), while no patients were found to carry DRB1*0402 (Dw10) or 0403 (Dw13). The frequency of the DRB1*0101 allele encoding DR1 was not increased, even among DR4-negative RA patients, and we were unable to detect any sharing of other class II alleles among DR4-negative patients. No contribution of any DQA1, DQB1, DPA1 or DPB1 alleles to RA susceptibility could be detected. The results suggest that in the Norwegian population RA is primarily associated with a shared sequence at residues 67-74 of the DR beta 1 chain, but only when this sequence is expressed on DR4 molecules.     

The majority of human CD3 epitopes are conferred by the epsilon chain

Transgenic mouse T cells expressing the human CD3 chain bindthe majority (29/36) of monoclonal antibodies (mAbs) specificfor human CD3. A proportion of these mAbs are also able to recognizeisolated CD3 in a soluble, recombinant form. Thus, CD3 can confermost CD3 epitopes on the TCR-CD3 complex, but many determinantsmay require assembly of the complex for their formation. A numberot mAbs did not recognize -transgenic T cells and probably needother CD3 subunits for binding. CD3-specific mAbs from eachof the three groups defined here, as well as mAbs directed againstthe TCRß heterodimer, are all able to activate T cells.Therefore mAb attachment at several different sites on the TCR-CD3complex can give rise to activation signals. This suggests thatthe cross-linking function of mitogenic antibodies may be theirmost significant property, rather than the perturbation of aparticular ‘functional epitope’.